Flight testing of a vehicle such as an aircraft typically requires the mounting of a variety of test hardware on the vehicle. Such hardware may comprise, without limitation, various types of instrumentation such as accelerometers, transducers, sensors and probes. In addition, flight test hardware may also include electrical wiring which may be assembled into wiring bundles and which is used to interconnect the test instrumentation.
The mounting of such instrumentation and wiring bundles may be effectuated through the use of temporary mounting brackets positioned at various spacings on a mounting surface of the vehicle. The mounting brackets must be capable of supporting the instrumentation and wiring and of resisting the various loads encountered during testing such as aerodynamic loads, structural loads, dynamic and static loads and various other direct and indirect loads. Such indirect loads may be the result of manipulation of the wiring or hardware during testing such as during inspecting, replacing, adding or remove wiring or instrumentation.
Although mechanical fastening of the mounting brackets may provide a relatively strong and robust attachment to the mounting structure, mechanical fastening typically requires the formation of fastener holes in the structure followed by the installation of fasteners such as screws or bolts to secure the brackets to the mounting surface. Because the test article may be a production vehicle that must be returned to a clean production configuration (e.g., with little if any non-production structures or non-production structural variations) for delivery to a customer following the completion of testing, mechanical fastening of temporary mounting brackets is typically avoided.
An alternative to mechanical fastening of mounting brackets may be adhesively bonding of temporary mounting brackets to the structure for supporting test hardware. Such adhesive bonding provides sufficient strength to support the mounting brackets without requiring the formation of extraneous fastener holes in the structure. Furthermore, adhesive bonding of brackets to the structure reduces the impact of testing on production flow wherein the testing may require an interruption of vehicle assembly while the vehicle is converted to a test configuration.
Although adhesively bonded brackets provide several advantages such as those associated with returning the vehicle to a clean production configuration, the conventional method of bonding such brackets presents several disadvantages which detract from its overall utility. For example, time constraints imposed by an aggressive test and/or production schedule may necessitate the use of adhesives having rapid cure times for bonding brackets to structure.
Although a rapid cure time may reduce the time required to convert the production vehicle into the test configuration, the performance characteristics of quick-curing adhesives may be relatively limited as compared to the performance characteristics of an optimal adhesive for a given application. Such performance characteristics may include a limited operating or service temperature or unfavorable peel strength and/or shear strength of the cured adhesive. Furthermore, the use of quick-curing adhesives with higher bond strengths may have undesirable results on the adhered-to structure when removed.
In an attempt to avoid undesirable results during removal of adhesively bonded brackets, a measured amount of heat may be applied to areas of the mounting surface around the bracket. Such heat may be applied using a heat gun which allows the user to direct a concentrated flow of hot air onto the bracket and to areas of the mounting surface surrounding the bracket in an attempt to soften the adhesive and reduce the bond strength such that the bracket may be more easily removed.
Unfortunately, most of the heat that is applied by the heat gun is drawn by the bracket and the structure upon which the bracket is mounted, especially composite structures as they may have a greater capacity for thermal conductance than the adhesive. As a result, little heat goes into the adhesive such that attempts to remove the bracket without sufficiently softening the adhesive can have undesirable results. In addition, because structures upon which the bracket is mounted and especially composite structures are limited in the amount of heat they can withstand, low heat gun settings or temperatures are required when attempting to remove an adhesively bonded bracket. The lower temperature settings required on the heat gun increases the amount of total time required to remove brackets and adhesive residue from the structure.
As can be seen, there exists a need in the art for a system and method for facilitating the removal of adhesively bonded brackets from a structure such that following testing, the vehicle can be converted from a test configuration back to a clean production configuration for delivery to the customer. Furthermore, there exists a need in the art for a system and method for facilitating the removal of adhesively bonded brackets in a reduced amount of time. In this regard, there exists a need in the art for a system and method for facilitating the removal of adhesively bonded brackets from a structure without undesirably affecting the structure upon which the bracket is mounted. Finally, there exists a need in the art for a system and method which can effectuate a reduction in adhesive cure time such that an optimal adhesive having the desired performance characteristics may be selected from a wide range of adhesives without the constraint of a rapid cure time.